Outer cutting blade for electric dry shaver

ABSTRACT

An outer cutting blade for use with electric dry shavers employing rotary type inner cutting blade, which comprises a plurality of spiral rib portions respectively extending from the center to the vicinity of outer periphery of the blade, and a plurality of hair inlet holes provided between the respective adjacent ones of said spiral rib portions. The holes are so arranged that their longitudinal direction will substantially coincide with the radial direction of the blade.

United States Patent Sakai et al.

OUTER CUTTING BLADE FOR ELECTRIC DRY SHAVER Inventors: Satoshi Sakai, Hirakata; Norio Shimizu, Neyagawa; Junji Nomura, Takatsuki, all of Japan Assignee: Matsushita Electric Works, Ltd.,

Osaka, Japan Notice: The portion of the term of this patent subsequent to June 17, 1992, has been disclaimed.

Filed: Sept. 10, 1973 Appl. No.: 395,403

Foreign Application Priority Data Sept. 13.1972 Japan 47-92442 Nov. 9, 1972 Japan 47-129080[U] US. Cl 30/43.6; 30/346.51 Int. Cl. B26B 19/14 Field of Search 30/434, 43.5, 43.6, 346.51

References Cited UNITED STATES PATENTS 5/l938 Moskovics 30/34651 X ]*Nov. 18, 1975 2,677,885 5/1954 Chaun 30/416 X 2,742,694 4/1956 Stone EEO/346.51 X

FOREIGN PATENTS OR APPLICATIONS 560,067 3/1957 Italy ..30/346.51 961,649 5/1950 France ..30/346.5l

Primary E.\'aminerJames L. Jones, Jr.

Assistant Examiner-Gary L. Smith Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[57] ABSTRACT An outer cutting blade for use with electric dry shavers employing rotary type inner cutting blade, which comprises a plurality of spiral rib portions respectively extending from the center to the vicinity of outer periphery of the blade, and a plurality of hair inlet holes provided between the respective adjacent ones of said spiral rib portions. The holes are so arranged that their longitudinal direction will substantially coincide with the radial direction of the blade.

5 Claims, 6 Drawing Figures Patent Nov. 18, 1975 Sheet2of3 3,919,770

WWW/ff HUM SEGDEQ wim] US. Patent Nov.18,1975 Sheet30f3 3,919,770

OUTER CUTTING BLADE FOR ELECTRIC DRY SHAVER This invention relates to outer cutting blades for electric dry shavers. v

For the outer cutting blade for conventional electric shavers, there have been used, for example, such net blade A wherein hair inlet holes a. are made in the form of a net as shown in FIG. 1 or such outer cutting blade A" wherein hair inlet holes a' are arranged on concentric circles as shown in FIG. 2. However, the net blade A shown in FIG. 1 has defects that, as the holes a are hexagonal, long hairs are hard to be led into these holes, the opening rate, that is, the rate of the area of the holes to the total surface area of the net blade is small, the rib b between the respective holes a is narraow in some part and, therefore, the strength against the external pressing force is low. The outer cutting blade A" shown in FIG. 2' has defects that, as the positions of the hair'inlet holes a" and ribs 17'. are constant with respect to the rotary inner 'cutting'blade (not shown), the parts in which the inner cutting blade is worn and the parts in which the inner blade is broken will partially occur to reduce the life of the inner cutting blade and, in case an external pressing force is applied to the vicinity the center of the outer cutting blade, the ribs b" on the concentric circles will not perform the role as of ribs and the strength will be low.

According to the present invention, the above mentioned problems have been successfully solved by providing several spiral ribs in the outer peripheral direction from the center in the outer cutting blade and forming hair inlet holes betwen the adjacent ribs in such that the lengthwise direction of each hole will substantially coincide with the radial direction of the outer cutting blade.

The present invention has such excellent features that:

a. The nearer to the outer periphery, the larger the holes in the outer cutting blade and the nearer to the center, the smaller the holes can be made. Therefore, both long and short hairs can be shaved efficiently and thus the hair shaving efficiency can be made high.

b. The angle of the intersection of the side edge of the hair inlet hole in the outer blade with the rotary inner blade, that is, cutting blade angle can be made constant for each hole and, therefore, the cutting blade angle in any position can be set at a desirable value.

c. As the ribs are spirally formed and the hair inlet holes are provided between the ribs, when the inner cutting blade rotates, it will contact the outer cutting blade uniformly in any part, so that the inner blade will be neither partially broken nor worn and will be able to be made long in the life.

d. Because of the spiral nature of the ribs the stationary blade is made stronger and more resistant to forces normal to the blade as compared to a blade having an overall net pattern or one in which the ribbing is concentric such as in the prior art illustrated in FIGS. 1 and 2.

The present invention shall be explained in detail with reference to certain preferred embodiments shown in the accompanying drawings, in which:

FIGS. I and 2 show outer cutting blades for conventional dry shavers;

FIG. 3 shows an embodiment of the outer cutting blade for the dry shavers according to the present invention;

FIG. 4 shows another embodiment of the present invention; and I FIGS. 5 and 6 are explanatory views of the cutting blade angle according to the present invention.

While the present invention shall be explained in the following with reference to the drawings, the intention is not to limit the invention to the particular embodiments illustrated, but rather to include all possible modifications, alterations and equivalent arrangements covered the'the scope of the appended claims.

Referring to FIG. 3 showing an outer cutting blade for the electric dry shavers of the present invention, A is a blade surface, a plurality of spiral ribs b are made in the outer peripheral direction from the center on said surface A and hair inlet holes a are formed between the adjacent ribs in the form of slits whose lengthwise direction substantially coincides with the radial direction of the outer cutting blade.

In FIG. 4 showing another embodiment of the present invention, hair inlet holes 0 of a fixed length are formed at regular intervals to form a ring adjacent the outer peripheral side of the blade surface A, plurality of spiral ribs b are made in the outer peripheral direction from the center between the outer peripheral inlet holes c on the adjacent ring and the center of the blade surface, and inlet holes a are made so that the so-called holding angle 6 made by the cutting edge line d of the inner cutting blade D rotating while in contact with the outer cutting blade inside the outer cutting blade and the side in the lengthwise direction of each inlet hole a will be always constant in any position as shown in FIG. 5 between the adjacent spiral ribs b. The length in the lengthwise direction of the inlet hole a is made gradually shorter, the longer diameter L and shorter diameter L of the respective holes a are made inversely proportional with each other, and both ends of the respective inlet holes a are formed to be substantially arcuate. In such formation, (i) the hair holding angle formed by the inner cutting blade edge and the edge of the respective holes in the outer cutting blade is constant in any place and, if an optimum holding angle 6 (of about 20) at which the hair cutting efficiency is the highest is adopted, the cutting efficiency of the entire surface of the blade will be able to be improved, (ii) as the dimensions of the longer diameter and shorter diameter of the respective holes over the blade are made inversely proportional with each other, hairs can be led in and can be cut to be short without biting skin surface or irritating skins.

In working the present invention, it is not necessary that the entire zone of the outer cutting blade surface should have the above described pattern but, if the rate occupied by the above described pattern is more than 50%, the priviledge by the present invention will be able to be enjoyed.

To summarize the disclosure, a circular stationary blade in the form of a thin metallic membrane is provided as illustrated particularly in FIGS. 3 and 4. Cooperating with the stationary blade is a rotary blade having a generally radially oriented cutting edge. The stationary blade is distinguished by a plurality of uniopening spanning the space between adjacent ribs and extending in a generally radial direction. The ribs are more closely spaced as they spiral inwardly toward the center, with the length of the openings being correspondingly reduced in the central region. More specifically, the openings each have their longitudinal dimension oriented to produce a shallow shearing angle with respect to the cutting edge of the blade, the shearing angle being preferably on the order of It is one of the features of the embodiment shown in FIG. 3 that each rib is of limited arcuate length, preferably on the order of 180 but in any event less than a full revolution. Finally, it is one of the features of the embodiment shown in FIG. 4 that the spacing between the ribs decreases as the periphery is approached thereby to provide a periphery of smoothly circular contour.

we claim:

1. A cutting blade assembly for a dry shaver including a circular stationary blade in the form of a thin metallic membrane and a rotating blade having a generally radially oriented cutting edge rotating concentrically against the stationary blade, the stationary blade having a plurality of uniformly interfitting smoothly continuous spiral ribs, adjacent ribs having formed between them a plurality of elongated hair inlet openings with adjacent openings closely spaced generally parallel to one another and with the longitudinal dimension of each opening spanning the space between adjacent ribs, the ribs being more closely spaced as they spiral inwardly toward the center with the length of the openings being correspondingly reduced, the openings having a slight incremental angle between them so that ad jacent openings bear substantially the same shallow angle with respect to the blade, with the longitudinal dimension of each opening extending in a symmetrically angled but generally radial direction.

2. The combination as claimed in claim 1 in which the openings each have their longitudinal dimension oriented to produce a shallow shearing angle with respect to the cutting edge of the blade and in which the shearing angle is on the order of 20.

3. The combination as claimed in claim 1 in which the spacing between the ribs increases uniformly from a small value at the center and progressing outwardly therefrom.

4. The combination as claimed in claim 3 in which each rib has an arc of at least about but less than 360.

5. The combination as claimed in claim 1 in which the spacing between the ribs decreases again as the periphery is approached thereby to provide a periphery of smoothly circular contour. 

1. A cutting blade assembly for a dry shaver including a circular stationary blade in the form of a thin metallic membrane and a rotating blade having a generally radially oriented cutting edge rotating concentrically against the stationary blade, the stationary blade having a plurality of uniformly interfitting smoothly continuous spiral ribs, adjacent ribs having formed between them a plurality of elongated hair inlet openings with adjacent openings closely spaced generally parallel to one another and with the longitudinal dimension of each opening spanning the space between adjacent ribs, the ribs being more closely spaced as they spiral inwardly toward the center with the length of the openings being correspondingly reduced, the openings having a slight incremental angle between them so that adjacent openings bear substantially the same shallow angle with respect to the blade, with the longitudinal dimension of each opening extending in a symmetrically angled but generally radial direction.
 2. The combination as claimed in claim (9) 1 in which the openings each have their longitudinal dimension oriented to produce a shallow shearing angle with respect to the cutting edge of the blade and in which the (shallow) shearing angle is on the order of 20*.
 3. The combination as claimed in claim 1 in which the spacing between the ribs increases uniformly from a small value at the center and progressing outwardly therefrom.
 4. The combination as claimed in claim 3 in which each rib has an arc of at least about 180* but less than 360*.
 5. The combination as claimed in claim 1 in which the spacing between the ribs decreases again as the periphery is approached thereby to provide a periphery of smoothly circular contour. 